Vehicular power source unit

ABSTRACT

Provided is a vehicular power source unit having an external electric power supply controlling element ( 94 ) configured to control the operation of a heater ( 16 ) and a recharger ( 22 ) operated by an electric power supplied from a commercial power source ( 70 ) via an external power source connector ( 25 ) according to a terminal voltage and temperature of a fuel cell ( 10 ) detected by a fuel cell state detecting element ( 91 ) and a state of a battery ( 20 ) detected by a battery state detecting element ( 92 ) when a fuel cell vehicle is halted, the supply of reactant gas to the fuel cell ( 10 ) by a fuel cell controlling element ( 93 ) is stopped and the external power source connector ( 25 ) is connected to the commercial power source ( 70 ).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a vehicular power source unit having afuel cell.

2. Description of the Related Art

Conventionally, there has been known a vehicular power source unit (forexample, refer to Japanese Patent Laid-open No. 2005-317410) which isprovided with a fuel cell and an auxiliary power source (a battery, acapacitor or the like) and is configured to operate a heater to heat thefuel cell with the electric power supplied from the auxiliary powersource at a low temperature.

In the conventional vehicular power source unit, after a given timeinterval has elapsed from the halt of a vehicle, the hydrogen in thefuel cell is scavenged and power generation from the fuel cell issuspended. In this case, when the hydrogen is supplied to the fuel cellto restart the power generation from the fuel cell, it will take sometime to raise the voltage generated from the fuel cell until stable.

Moreover, if the power generation from the fuel cell is restarted at alow temperature, it will take additional time to raise the temperatureof the fuel cell to an appropriate temperature. Therefore, the timeneeded to raise the voltage generated from the fuel cell until stablewill become further longer.

If the vehicle is started before the temperature of the fuel cell hasbeen sufficiently raised, the electric current supplied from the fuelcell will become greater, which in turn decrease the voltage generatedfrom the fuel cell drastically. Consequently, the component materials ofthe fuel cell are deteriorated, which degrades the performance of thefuel cell.

Thus, before the generated voltage from the fuel cell is raised untilstable, it is required to assist the fuel cell with electric powersupplied from the auxiliary power source to run the vehicle. However, inthis case, if an amount of charge of the auxiliary power source isinsufficient, the fuel cell may not be sufficiently assisted by theauxiliary power source, which leads to a problem that it will take alonger time for the total power output from the fuel cell and theauxiliary power source to reach a level required to run the vehicle.

SUMMARY OF THE INVENTION

The present invention has been accomplished in view of theaforementioned problems, and it is therefore an object of the presentinvention to provide a vehicular power source unit capable of shorteninga time interval for a total power output from a fuel cell and anauxiliary power source to reach a level required to run a vehicle whenthe fuel cell is operated to generate electric power to run the vehicle.

To attain an object described above, the present invention provides avehicular power source unit mounted in a vehicle for supplying electricpower to an electric load disposed in the vehicle.

The vehicular power source unit of the present invention is providedwith a fuel cell; a fuel cell controlling element configured to controlthe supply of reactant gas to the fuel cell; an electric accumulator; anexternal power source connector for detachably connecting to an externalpower source; a heater operated by the electric power supplied from theexternal power source via the external power source connector to heatthe fuel cell; a recharger operated by the electric power supplied fromthe external power source via the external power source connector tocharge the electric accumulator; a fuel cell state detecting elementconfigured to detect a state of the fuel cell; an electric accumulatorstate detecting element configured to detect a state of the electricaccumulator; and an external electric power supply controlling elementconfigured to control the operation of the heater and the rechargeroperated by the electric power supplied from the external power sourcevia the external power source connector according to the state of thefuel cell detected by the fuel cell state detecting element and thestate of the electric accumulator detected by the electric accumulatorstate detecting element when the vehicle is halted, the supply of thereactant gas to the fuel cell by the fuel cell controlling element isstopped and the external power source connector is connected to theexternal power source.

According to the present invention, when the vehicle is halted, thevehicular power source unit can be supplied with electric power from theexternal power source connected via the external power source connector.Further, the state of the fuel cell is detected by the fuel cell statedetecting element and the state of the electric accumulator is detectedby the electric accumulator state detecting element.

When the vehicle is halted, the supply of the reactant gas to the fuelcell by the fuel cell controlling element is stopped and the externalpower source connector is connected to the external power source, theexternal power source supply controlling element, according to the stateof the fuel cell detected by the fuel state detecting element and thestate of the electric accumulator detected by the electric accumulatorstate detecting element, controls the operation of the heater and therecharger powered by the electric power supplied from the external powersource via the external power source connector. Accordingly, theelectric power supplied from the external power source via the externalpower source connector can be efficiently allocated for heating the fuelcell and for charging the electric accumulator according to the state ofthe fuel cell and the electric accumulator.

Heating the fuel cell can make the electric power generated from thefuel cell increase rapidly when the supply of the reactant gas to thefuel cell is initiated. Charging the electric accumulator can offerincreased amount of charge in the electric accumulator for future use.Thereby, when the fuel cell is operated to generate electric power torun the vehicle, the electric power generated from the fuel cell can berapidly increased and the assisting electric power from the electricaccumulator can be assured, which makes it possible to shorten a timeinterval for a total power output from the fuel cell and the electricaccumulator to reach a level required to run the vehicle.

The fuel cell controlling element performs a scavenging action whichscavenges the reactant gas remained in the fuel cell at a predefinedtiming after the supply of the reactant gas to the fuel cell is stopped;the fuel cell state detecting element determines whether or not thescavenging action has been performed on the fuel cell and detects thetemperature of the fuel cell; and the external electric power supplycontrolling element prohibits the heating of the fuel cell by the heaterand performs the charging of the electric accumulator by the rechargerif the scavenging action has not been performed on the fuel cell, andperforms the heating of the fuel cell by the heater and the charging ofthe electric accumulator by the recharger if the scavenging action hasbeen performed on the fuel cell and if the temperature of the fuel cellis equal to or lower than a predefined temperature when the vehicle ishalted, the supply of the reactant gas to the fuel cell by the fuel cellcontrolling element is stopped and the external power source connectoris connected to the external power source.

According to the present invention, even though the supply of thereactant gas to the fuel cell is stopped, the heating of the fuel cellwith the heater is not required since the fuel cell is generating heatif the scavenging action is not performed. Thereby, the externalelectric power supply controlling element controls the recharger tocharge the electric accumulator.

On the other hand, after the scavenging action has been performed on thefuel cell, the temperature of the fuel cell will decline. In this case,when the temperature of the fuel cell becomes equal to or lower than thepredefined temperature, by performing both the heating of the fuel cellwith the heater and the charging of the electric accumulator with therecharger, it is expected to prevent the temperature from declining soas to shorten the warming time when the fuel cell is restarted togenerate electric power with the electric accumulator being chargedmeanwhile.

Further, the electric accumulator state detecting element detects atemperature and an amount of charge of the electric accumulator as thestate of the electric accumulator; and the external electric powersupply controlling element varies a magnitude of a charging currentsupplied to the electric accumulator from the recharger according to thetemperature and the amount of charge of the electric accumulatordetected by the electric accumulator state detecting element.

According to the present invention, the charge performance of theelectric accumulator varies in accordance with the temperature and theamount of charge thereof. Thereby, the external electric power supplycontrolling element varies the magnitude of charging current suppliedfrom the recharger to the electric accumulator according to thetemperature and the amount of charge of the electric accumulator.Accordingly, the deterioration of the electric accumulator due toexcessive current supplied thereto when it is charged can be avoided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overall configuration diagram of a vehicular power sourceunit according to an embodiment of the present invention.

FIG. 2 is a flow chart illustrating a processing order of heating of afuel cell and charging of a battery with an external power source supplycontrolling element illustrated in FIG. 1.

FIG. 3 is a flow chart illustrating a processing order of heating of thefuel cell and charging of the battery with the external power sourcesupply controlling element illustrated in FIG. 1.

FIG. 4 is a flow chart illustrating processing effects by the externalpower source supply controlling element.

FIG. 5( a) and FIG. 5( b) are diagrams illustrating state variations ofthe fuel cell and the battery treated by the external power sourcesupply controlling element when the external power source connector isconnected to the commercial power source after a scavenging action hasbeen performed on the fuel cell.

FIG. 6( a) and FIG. 6( b) are diagrams illustrating state variations ofthe fuel cell and the battery treated by the external power sourcesupply controlling element when the external power source connector isconnected to the commercial power source before the scavenging action isperformed on the fuel cell.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, an embodiment of the present invention will be described indetail with reference to FIG. 1 to FIG. 6. FIG. 1 illustrates aconfiguration diagram of a vehicular power source unit 1 in the presentembodiment. The vehicular power source unit 1 is mounted in a fuel cellvehicle (equivalent to a vehicle of the present invention) havingdriving wheels (not shown) thereof driven by a motor 41.

Referring to FIG. 1, the vehicular power source unit 1 is provided witha fuel cell 10, a battery 20 (equivalent to an electric accumulator ofthe present invention), a recharger 22 for charging the battery 20, anexternal power source connector 25 which is detachably connected to acommercial power source (equivalent to an external power source of thepresent invention), a DC/DC converter 30 connected between the fuel cell10 and the battery 20, an inverter 40 connected with the fuel cell 10and the DC/DC converter 30 for outputting electric power to run a motor41, a coolant circulation circuit 50 connected to a coolant passagebetween the fuel cell 10 and the inverter 40, a pump 52 circulatingcoolants in the coolant circulation circuit 50, and a controller 90controlling the overall operation of the vehicular power source unit 1.

The fuel cell 10 is provided with a fuel cell sensor 11 for detecting atemperature, a terminal voltage, an output current, a supply pressure ofreactant gases (in the present embodiment, they are hydrogen and air)and the like of the fuel cell 10, a circulation valve 12 disposed at aconnection point between the coolant circulation circuit 50 and the fuelcell 10, an air valve 13 disposed in an air supply pipe, a hydrogenvalve 14 disposed in a hydrogen supply pipe, a heater 16, a circulationvalve 15 disposed at a connection point between the heater 16 and thefuel cell 10, a drain valve 17 disposed between the fuel cell 10 and adrain pipe of a drain 18.

The battery 20 is provided with a battery sensor 21 for detecting atemperature, a terminal voltage, an output current and the like of thebattery 20. The battery 20 is also connected with an air conditioner 60and a down converter 61 connected with a load of 12V. In the load of12V, a fuel cell auxiliary device (not shown) for supplying the reactantgases (air and hydrogen) to the fuel cell 10 is included.

The controller 90 is an electronic unit composed of a micro computer(not shown) and the like. By executing a control program for thevehicular power source unit 1 in the micro computer, the controller 90functions as a fuel cell state detecting element 91, a battery statedetecting element 92, a fuel cell controlling element 93, and anexternal electric power supply controlling element 94.

Detection signals of the temperature, the terminal voltage, the outputcurrent, the supply pressure of reactant gases and the like of the fuelcell 10 detected by the fuel cell sensor 11, and detection signals ofthe temperature, the terminal voltage, the output current and the likeof the battery 20 detected by the battery sensor 21 are input into thecontroller 90. The circulation valves 12, 15 and 42, the air valve 13,the hydrogen valve 14, the heater 16, the drain valve 17, the DC/DCconverter 30, the recharger 22, the pump 52, and the fuel cell auxiliarydevice are controlled according to control signals output from thecontroller 90.

The fuel cell state detecting element 91, on the basis of the detectionsignals output from the fuel cell sensor 11, detects the temperature,the terminal voltage, the output current, the supply pressure ofreactant gases and the like of the fuel cell 10. As to be describedhereinafter, the fuel cell state detecting element 91, on the basis ofthe terminal voltage of the fuel cell 10, determines whether or not ascavenging action which scavenges hydrogen in the fuel cell 10 has beenperformed.

The battery state detecting element 92, on the basis of the detectionsignals output from the battery sensor 21, detects the temperature, theterminal voltage, the output current, the SOC (State of Charge: thepercentage of the amount of residual charge of the battery 20 when theamount of charge in the full-charged battery 20 is denoted as 100%) andthe like of the battery 20.

The fuel cell controlling element 93 controls the amount of reactantgases supplied to the fuel cell 10 so as to generate a desired electricpower from the fuel cell 10. The desired electric power generated fromthe fuel cell 10 is determined by an ECU (abbreviation of ElectricControl Unit, not shown) which controls the overall operation of thefuel cell vehicle. Moreover, the fuel cell controlling element 93performs the scavenging action to scavenge hydrogen remained in the fuelcell 10 when the supply of reactant gases to the fuel cell 10 issuspended to stop the fuel cell 10 from generating electric power.

When the fuel cell vehicle is halted and the commercial power source 70is connected to the external power source connector 25, the externalelectric power supply controlling element 94 allocates the electricpower supplied from the commercial power source 70 for charging thebattery 20 through the recharger 22 and for operating the heater 16 toheat the fuel cell 10.

Hereinafter, with reference to the flow charts illustrated in FIG. 2 andFIG. 3, respectively, the description will be carried out on theprocessing performed by the external electric power supply controllingelement 94.

In FIG. 2, when the commercial power source 70 is connected to theexternal power source connector 25 at STEP 1, the process moves to STEP2 where the external electric power supply controlling element 94determines whether the terminal voltage of the fuel cell 10 detected bythe fuel cell state detecting element 91 is equal to or less than 0.5Vor not.

Herein, the terminal voltage of 0.5V is a threshold used to determinewhether or not the scavenging action has been performed after the supplyof reactant gases to the fuel cell 10 is suspended. If the hydrogenremained in the fuel cell 10 has been scavenged by the scavengingaction, the electric power generated by the fuel cell 10 declines; thus,the terminal voltage of the fuel cell 10 will drop to around 0V.Thereby, if the terminal voltage of the fuel cell 10 becomes equal to orless than 0.5V, it can be determined that the scavenging action has beenperformed.

When the terminal voltage of the fuel cell 10 becomes equal to or lessthan 0.5V (i.e. the scavenging action has been performed), the processmoves to STEP 3 where the external electric power supply controllingelement 94 determines whether or not the temperature of the fuel cell 10is lower than −10° C. (equivalent to a predefined temperature of thepresent invention). Herein, if the temperature of the fuel cell 10 islower than −10° C., water produced from the power generation freezes inthe supply passage supplying the reactant gases to the fuel cell 10,which deteriorates the power generation performance of the fuel cell 10.

If the temperature of the fuel cell 10 is determined to be lower than−10° C., the process moves to STEP 4. As illustrated in FIG. 2, theprocessing at STEP 6, STEP 10 and STEP 20, respectively, is configuredto heat the coolants in the circulation circuit 50 with the heater 16,supply the heated coolants through the coolant passage of the fuel cell10 with the pump 52 to warm up the fuel cell 10, and charge the battery20 at the same time.

At STEP 4, the external electric power supply controlling element 94determines whether or not the temperature of the battery 20 detected bythe battery state detecting element 92 is higher than 0° C. If thetemperature of the batter 20 is determined to be higher than 0° C.(without deteriorating the charge performance of the battery 20), theprocess moves to STEP 5 where the external electric power supplycontrolling element 94 determines whether or not the SOC of the battery20 detected by the battery state detecting element 92 is lower than 20%.

At STEP 5, if the SOC of the battery 20 is determined to be lower than20%, in other words, the discharge performance of the battery 20 is notdeteriorated by the low temperature and the amount of charge of thebattery 20 is insufficient, the process moves to STEP 6 where theexternal electric power supply controlling element 94 performs fastcharge on the battery 20 with a charging current greater than the normalcurrent flown from the recharger 22 into the battery 20 and initiatesthe heater 16. Thereby, when the amount of charge of the battery 20 isinsufficient, the battery 20 is fast charged, and meanwhile, the fuelcell 10 is heated to prevent the temperature thereof from dropping.

On the other hand, if the SOC of the battery 20 is determined to beequal to or greater than 20% at STEP 5, namely, the dischargeperformance of the battery 20 is not deteriorated by the low temperatureand the amount of charge of the battery 20 is sufficient, the processmoves to STEP 20 where the external electric power supply controllingelement 94 performs normal charge on the battery 20 through therecharger 22. Thereby, the battery 20 can be prevented from beingdeteriorated by fast charge performed when the amount of charge isinsufficient, and the fuel cell 10 is heated at the same time, whichprevents the temperature of the fuel cell 10 from dropping.

Further, at STEP 4, if the temperature of the battery 20 is determinedto be equal to or lower than 0° C., namely, the charge performance ofthe battery 20 has been deteriorated by the low temperature, the processdiverges to STEP 10 where the external electric power supply controllingelement 94 performs slow charge on the battery 20 with a chargingcurrent smaller than the normal current flown from the recharger 22 intothe battery 20. Thereby, the fuel cell 10 is heated to prevent thetemperature thereof from dropping.

If the terminal voltage of the fuel cell 10 is determined to be equal toor greater than 0.5V at STEP 2, since the scavenging action has not beenperformed on the fuel cell 10, the fuel cell 10 is generating heat.Therefore, it is not required to heat the fuel cell 10 with the heater16. Moreover, when the temperature of the fuel cell 10 is determined tobe equal to or higher than −10° C. at STEP 3, it is also not required toheat the fuel cell 10 with the heater 16.

Thus, either when the terminal voltage of the fuel cell 10 is equal toor greater than 0.5V at STEP 2 or when the temperature of the fuel cell10 is equal to or higher than −10° C. at STEP 3, the process diverges toSTEP 30 of FIG. 3. The processing at STEP 31, STEP 40 and STEP 50,respectively, is for charging the battery 20 by varying the magnitude ofthe charging current according to the temperature and the SOC of thebattery 20 without heating the fuel cell 10 via the heater 16.

At STEP 30, the external electric power supply controlling element 94determines whether or not the temperature of the battery 20 is higherthan 0° C. If the temperature of the battery 20 is determined to behigher than 0° C., the process moves to STEP 31 where the externalelectric power supply controlling element 94 determines whether or notthe SOC of the battery 20 is less than 20%.

If the SOC of the battery 20 is determined to be less than 20% at STEP31, namely, when the temperature of the battery 20 is equal to or higherthan 0° C. and the SOC of the battery 20 is less than 20%, the processmoves to STEP 32 where the external electric power supply controllingelement 94 performs fast charge on the battery 20 with a chargingcurrent greater than the normal current.

If the SOC of the battery 20 is determined to be equal to or greaterthan 20% at STEP 31, namely, when the temperature of the battery 20 isequal to or higher than 0° C. and the SOC of the battery 20 is equal toor greater than 20%, the process moves to STEP 50 where the externalelectric power supply controlling element 94 performs normal charge onthe battery 20. Accordingly, the battery 20 is charged.

On the other hand, if the temperature of the battery 20 is determined tobe equal to or lower than 0° C. at STEP 30, the process moves to STEP 40where the external electric power supply controlling element 94 performsslow charge on the battery 20 with a charging current smaller than thenormal current. Thereby, the battery 20 with the charge performancethereof degraded due to the low temperature can be charged.

After the battery 20 is charged at STEP 32, STEP 40 or STEP 50, theprocess moves to STEP 33 where the processing by the external electricpower supply controlling element 94 is ended. It should be noted thatthe external electric power supply controlling element 94 performs theprocessing illustrated in FIG. 2 and FIG. 3 iteratively if the fuel cellvehicle is halted.

FIG. 4 is a flow chart illustrating how a waiting time Tw where it isready for a driver to run the fuel cell vehicle after the driver turnson an ignition of the fuel cell vehicle while the above-mentionedprocesses in FIG. 2 and FIG. 3 are being performed by the externalelectric power supply controlling element 94 varies according to thetemperature of the fuel cell 10, the SOC of the battery 20, and thetemperature of the battery 20.

When the driver turns on the ignition at STEP 60, the supply of thereactant gases to the fuel cell 10 is performed by the fuel cellcontrolling element 93; however, in prior to this, the above-mentionedprocesses in FIG. 2 and FIG. 3 have been performed by the externalelectric power supply controlling element 94. Thereby, the battery 20 ischarged while the fuel cell 10 is being heated by the heater 16 inaccordance with the temperature of the fuel cell 10.

At STEP 61, if the temperature of the fuel cell 10 is determined to behigher than 0° C., it is possible for the fuel cell 10 to generate moreelectric power instantly since the fuel cell 10 is not needed to bewarmed up. Therefore, the waiting time Tw is zero (state 1).

If the temperature of the fuel cell 10 is determined to be equal to orlower than 0° C. at STEP 61, the process diverges to STEP 70. Further,at STEP 70, if the SOC of the battery 20 is determined to be smallerthan 20%, the process diverges to STEP 80 (state 3).

On the contrary, if the SOC of the battery 20 is determined to begreater than 20% at STEP 70, the process moves to STEP 71. If thetemperature of the battery 20 is determined to be lower than 0° C., theprocess moves to STEP 80 (state 3); and if the temperature of thebattery 20 is determined to be equal to or higher than 0° C., theprocess diverges to STEP 72 (state 2).

In the state 2 of STEP 72, since the amount of charge in the battery 20is sufficient and the temperature of the battery 20 is high (0° C. orhigher than 0° C.), the battery 20 can continue to generate electricpower in a duration Tes. Therefore, the waiting time Tw=Tfc−Tes.

In the state 3 of STEP 80, either the amount of charge in the battery 20is less or the temperature of the battery is low, the dischargeperformance of the battery is degraded, the duration Tes where thebattery 20 can continue to generate electric power equals to zero.Moreover, since the temperature of the fuel cell 10 is low (lower than0° C.), it is required to warm up the fuel cell 10. Therefore, thewaiting time Tw equals to the warming time Tfc of the fuel cell 10.

As mention above, when the fuel cell vehicle is halted and thescavenging action has been performed on the fuel cell 10, the state 2 ofSTEP 72 in FIG. 4 can be achieved through the processes performed by theexternal electric power supply controlling element 94 according to theflow charts illustrated in FIG. 2 and FIG. 3.

Conventionally, the waiting time Tw in state 3 is equal to Tfc (warmingtime for the fuel cell) when the ignition is turned on after thescavenging action has been performed on the fuel cell 10. However,according to the present embodiment, the waiting time Tw can beshortened as (Tfc−Tes), namely, the state 2.

Hereinafter, with reference to FIG. 5( a), FIG. 5( b), FIG. 6( a) andFIG. 6( b), the description will be carried out on the state variationof the fuel cell 10 and the battery 20 when the ignition is turned ontill the total electric power required to run the fuel cell vehicle isobtained from the fuel cell 10 and the battery 20.

The graphs illustrated in FIG. 5( a) and FIG. 5( b) illustraterespectively a case where the commercial power source 70 is connected tothe external power source connector 25 after the scavenging action hasbeen performed on the fuel cell 10. The vertical axes denote temperature(left side) and output electric power (right side), and the horizontalaxis denotes time.

In FIG. 5( a), t₁₀ denotes a time where the scavenging action wasperformed on the fuel cell 10, t₁₁ denotes a time where the normalcharge on the battery 20 was started, t₁₂ denotes a time where theheating of fuel cell 10 by the heater 16 was started, and t₁₄ denotes atime where the slow charge on the battery 20 was initiated.

The state variation of the fuel cell 10 and the battery 20 after theignition was turned on at Time=3 (sec) as illustrated in FIG. 5( a) isdenoted as the state variation thereof at Time=0 in FIG. 5( b).

In FIG. 5( a) and FIG. 5( b), Tf denotes the temperature of the fuelcell 10, Te denotes the temperature of the battery 20, Pf denotes theoutput electric power (generated electric power) from the fuel cell 10,Pe denotes the output electric power from the battery 20, and Pt denotesthe total electric power (Pt=Pf+Pe) output from the fuel cell 10 and thebattery 20.

Referring to FIG. 5( a), when the supply of reactant gases to the fuelcell 10 is stopped at Time=0, the temperature Tf of the fuel cell 10 andthe output electric power Pf thereof fall accordingly. In response, thetemperature Te and the output electric power Pe of the battery 20decrease.

Thereafter, when the scavenging action is performed on the fuel cell 10at t₁₀, the temperature Tf and the output electric power Pf of the fuelcell 10 drastically decrease. Then, at t₁₁, the normal charge on thebattery 20 is initiated according to STEP 50 of FIG. 3, and at t₁₂ wherethe temperature of the fuel cell 10 became lower than −10° C., the fuelcell 10 is heated by the heater 16 according to STEP 20 of FIG. 2.Thereby, the temperature of the fuel cell 10 is maintained around −10°C. after t₁₂.

At t₁₄ where the temperature of the battery 20 becomes equal to or lowerthan 0° C. after the normal charge, the charging of the battery 20 isswitched from the normal charge into the slow charge according to STEP10 in FIG. 2.

Referring to FIG. 5( b), when the supply of reactant gases to the fuelcell 10 is initiated, the output electric power Pf from the fuel cell 10drastically increases, and the temperature of the fuel cell 10 increasesfrom around −10° C. to around 0° C. On the other hand, the outputelectric power from the battery 20 decreases in relation to theincrement of the output electric power from the fuel cell 10.

When the total electric power Pt of the output electric power Pf fromthe fuel cell 10 and the output electric power Pe from the battery 20reaches the value sufficient to run the fuel cell vehicle, for example,30 (kW), the waiting time Tw is 7.6 seconds.

On the other hand, if the processes in FIG. 2 and FIG. 3 were notperformed by the external electric power supply controlling element 94,when the ignition is turned on at the condition where the SOC of thebattery 20 is equal to or smaller than 20% and the temperature of thefuel cell 10 is lower than −10° C., the fuel cell 10 must be heated,which corresponds to the state 3 of STEP 80 illustrated in FIG. 4.Therefore, the waiting time Tw becomes equal to or greater than, forexample, 13 seconds.

The graphs illustrated in FIG. 6( a) and FIG. 6( b) illustraterespectively a case where the commercial power source 70 is connected tothe external power source connector 25 before the scavenging action isperformed on the fuel cell 10. Similar to FIG. 5( a) and FIG. 5( b), thevertical axes denote temperature (left side) and output electric power(right side), and the horizontal axis denotes time.

In FIG. 6( a) and FIG. 6( b), Tf denotes the temperature of the fuelcell 10, Te denotes the temperature of the battery 20, Pf denotes theoutput electric power (generated electric power) from the fuel cell 10,Pe denotes the output electric power from the battery 20, and Pt denotesthe total electric power (Pt=Pf+Pe) output from the fuel cell 10 and thebattery 20.

In FIG. 6( a), t₂₀ denotes a time where the slow charge on the fuel cell10 is started after the commercial power source 70 is connected to theexternal power source connector 25, t₂₁ denotes a time where thescavenging action was performed on the fuel cell 10, t₂₂ denotes a timewhere the heating of fuel cell 10 by the heater 16 was started, and t₂₃denotes a time where the slow charge on the battery 20 was initiated.The state variation of the fuel cell 10 and the battery 20 after theignition was turned on at Time=3 (sec) as illustrated in FIG. 6( a) isdenoted as the state variation thereof at Time=0 in FIG. 6( b).

Referring to FIG. 6( a), when the supply of reactant gases to the fuelcell 10 is stopped at Time=0, the temperature Tf of the fuel cell 10 andthe output electric power Pf thereof fall accordingly. On the contrary,the output electric power Pe of the battery 20 increases in response tothe initiation of fast charge on the battery 20 according to STEP 32 ofFIG. 3 at t₂₀, and the temperature Te of the battery 20 is stable around20° C.

Thereafter, when the scavenging action is performed on the fuel cell 10at t₂₁, the temperature Tf and the output electric power Pf of the fuelcell 10 drastically decrease. Then, at t₂₂ where the temperature of thefuel cell 10 became lower than −10° C., the fuel cell 10 is heated bythe heater 16 according to STEP 20 of FIG. 2. Thereby, the temperatureof the fuel cell 10 is maintained around −10° C. after t₂₂.

At t₂₃ where the SOC of the battery 20 becomes equal to or greater than20%, the charging of the battery 20 is switched from the fast chargeinto the normal charge according to STEP 10 in FIG. 2.

With reference to FIG. 6( b), since the total electric power Pt of theoutput electric power Pf from the fuel cell 10 and the output electricpower Pe from the battery 20 surpasses the value sufficient to run thefuel cell vehicle, for example, (kW), the waiting time Tw becomes zerosecond.

As described above with reference to FIG. 5( a), FIG. 5( b), FIG. 6( a)and FIG. 6( b), according to the processes performed in the flow chartsillustrated in FIG. 2 and FIG. 3, respectively, the waiting time Tw forobtaining the necessary electric power to run the fuel cell vehicleafter the ignition is turned on can be shortened.

In the present embodiment, the terminal voltage and the temperature ofthe fuel cell 10 are detected by the fuel cell state detecting element91, and the external electric power supply controlling element 94determines whether to heat the fuel cell 10 with the heater 16 or not onthe basis of the terminal voltage and the temperature of the fuel cell10. However, it is acceptable to determine whether or not to heat thefuel cell 10 with the heater 16 on the basis of either the terminalvoltage of the fuel cell 10 only or the temperature of the fuel cell 10only.

In the present embodiment, the fuel cell state detecting element 91determines whether the scavenging action has been performed on the fuelcell 10 or not according to the terminal voltage of the fuel cell 10.However, if information related to the execution of the scavengingaction is transmitted between the fuel cell state detecting element 91and the fuel cell controlling element 93, it is acceptable for the fuelcell state detecting element 91 to determine whether the scavengingaction has been performed on the fuel cell 10 or not according to theinformation.

Further, in the present embodiment, the SOC and the temperature of thebattery 20 are detected by the battery state detecting element 92, andthe external electric power supply controlling element 94 switches modesamong the fast charge, the normal charge and the slow charge to chargethe battery 20 according to SOC and the temperature of the battery 20;however, the mode switching may be performed on the basis of either theSOC of the battery 20 only or the temperature of the battery 20 only.

Furthermore, in the present embodiment, the battery 20 is denoted as theelectric accumulator of the present invention; however, it is acceptableto use a capacitor as the electric accumulator.

1. A vehicular power source unit mounted in a vehicle for supplyingelectric power to an electric load disposed in the vehicle, comprising:a fuel cell; a fuel cell controlling element configured to control asupply of reactant gas to the fuel cell; an electric accumulator; anexternal power source connector for detachably connecting to an externalpower source; a heater operated by the electric power supplied from theexternal power source via the external power source connector to heatthe fuel cell; a recharger operated by the electric power supplied fromthe external power source via the external power source connector tocharge the electric accumulator; a fuel cell state detecting elementconfigured to detect a state of the fuel cell; an electric accumulatorstate detecting element configured to detect a state of the electricaccumulator; and an external electric power supply controlling elementconfigured to control the operation of the heater and the rechargeroperated by the electric power supplied from the external power sourcevia the external power source connector according to the state of thefuel cell detected by the fuel cell state detecting element and thestate of the electric accumulator detected by the electric accumulatorstate detecting element when the vehicle is halted, the supply of thereactant gas to the fuel cell by the fuel cell controlling element isstopped and the external power source connector is connected to theexternal power source.
 2. The vehicular power source unit according toclaim 1, wherein the electric accumulator state detecting elementdetects a temperature and an amount of charge of the electricaccumulator as the state of the electric accumulator; and the externalelectric power supply controlling element varies a magnitude of acharging current supplied to the electric accumulator from the rechargeraccording to the temperature and the amount of charge of the electricaccumulator detected by the electric accumulator state detectingelement.
 3. The vehicular power source unit according to claim 1,wherein the fuel cell controlling element performs a scavenging actionwhich scavenges the reactant gas remaining in the fuel cell at apredefined timing after the supply of the reactant gas to the fuel cellis stopped; the fuel cell state detecting element determines whether ornot the scavenging action has been performed on the fuel cell anddetects a temperature of the fuel cell; and the external electric powersupply controlling element prohibits the heating of the fuel cell by theheater and performs the charging of the electric accumulator by therecharger if the scavenging action has not been performed on the fuelcell, and performs the heating of the fuel cell by the heater and thecharging of the electric accumulator by the recharger if the scavengingaction has been performed on the fuel cell and if the temperature of thefuel cell is equal to or lower than a predefined temperature when thevehicle is halted, the supply of the reactant gas to the fuel cell bythe fuel cell controlling element is stopped and the external powersource connector is connected to the external power source.
 4. Thevehicular power source unit according to claim 3, wherein the electricaccumulator state detecting element detects a temperature and an amountof charge of the electric accumulator as the state of the electricaccumulator; and the external electric power supply controlling elementvaries a magnitude of a charging current supplied to the electricaccumulator from the recharger according to the temperature and theamount of charge of the electric accumulator detected by the electricaccumulator state detecting element.
 5. A vehicular power source unitfor a vehicle, said vehicular power source unit comprising: a heaterconfigured to be connected to an external power source, and configuredto heat a fuel cell; a recharger configured to be connected to theexternal power source, and configured to charge an electric accumulator;and an external electric power controlling element configured to controloperation of the heater and the recharger according to a state of thefuel cell and a state of the electric accumulator when a vehicle isstopped, when a supply of a reactant gas to the fuel cell stopped, andwherein an external power source connector is connected to the externalpower source.
 6. A method of controlling operation of a vehicular powersource unit, said method comprising: detecting a state of a fuel cellusing a fuel cell state detecting element; detecting a state of anelectric accumulator using an electric accumulator state detectingelement; determining that a vehicle powered by the vehicular powersource unit is stopped; determining that a supply of reactant gas to thefuel cell is stopped; determining that an external power source isconnected to the vehicular power source unit; and controlling operationof a heater and a recharger by electric power supplied from the externalpower source, based upon the state of the fuel cell and the state of theelectric accumulator.
 7. The method according to claim 6, furthercomprising: detecting a temperature and an amount of charge of theelectric accumulator as the state of the electric accumulator; andvarying a magnitude of a charging current supply to the electricaccumulator from the recharger according to the temperature and theamount of charge of the electric accumulator detected by the electricaccumulator state detecting element.
 8. A method according to claim 6,further comprising: scavenging the reactant gas remaining in the fuelcell at a predetermined time after the supply of reactant gas to thefuel cell is stopped; determining whether or not the scavenging has beenperformed on the fuel cell; detecting a temperature of the fuel cell;and if the scavenging has not been performed on the fuel cell,prohibiting heating of the fuel cell and charging of the electricaccumulator by the recharger, and, if the scavenging action has beenperformed on the fuel cell, heating the fuel cell by the heater andcharging the electric accumulator by the recharger; determining if thetemperature of the fuel cell is equal to or lower than a pre-definedtemperature when the vehicle is stopped, and stopping the supply ofreactant gas to the fuel cell by the fuel controlling element.
 9. Amethod according to claim 8, further comprising: detecting a temperatureand an amount of charge of the electric accumulator as the state of theelectric accumulator; and varying a magnitude of a charging currentsupply to the electric accumulator from the recharger according to thetemperature and the amount of charge of the electric accumulator.